Automate builds and release management

[jbergstroem]

Seeing how this repository is now closing in on a more reproducible and – if you are adventurous enough – stable build; there is also time to consider moving builds away from docker to here.

This means that:

• the repo should push commits w/ tags from master to docker hub
• the repo should tag latest at a push of a tag that resembles latest (not sure how to figure this out quite yet)